Experimental-numerical study on weakened HSS-to-HSS connections using HBS and RBS approaches

Abstract

Hollow structural sections (HSS) have been used more often as columns because of their symmetrical geometry and admissible performance in bearing axial forces along with bending and torsional moments. The use of hollow sections as beams in moment-resisting frames would be beneficial and is worthy to assess. To this aim and considering the importance of developing plastic bending hinges of the special moment-resisting frames in a zone far from the column face, two methods for weakening beam sections are studied and compared in this paper: 1) Reduced beam section (RBS) and 2) Heat-treated beam section (HBS). For the experimental investigation, a furnace was first made to heat the desired zone of the beam. Then, a cyclic quasi-static loading protocol was applied to two full-scale beam-column connection specimens. The experimental specimens were made by box sections in which the beams had reduced or heat-treated sections. Moreover, for verification and parametric studies, finite element models were generated using ABAQUS. The columns of numerical models had box sections whereas rectangular and circular hollow structural sections were used as beams. Additionally, the seismic behavior of two beam-column connection models with box and pipe heat-treated beam sections was investigated under near-field loading protocol. Compared with RBS sections, both the results of experimental and numerical studies indicated the acceptable bending behavior of heat-treated hollow structural sections in terms of prevention of lateral-torsional buckling along with a stable hysteretic behavior.